Leukocytes are a type of white blood cell. When urine is positive for leukocytes, there are leukocytes in the urine. White blood cells in urine are typically a sign of infection. A urinalysis positive for leukocytes is most commonly the result of a kidney infection, cystitis or urethritis.

+++ And 500 denotes is the number and quantity.

This indicates that the number is significant.

Please visit your doctor at the earliest and get your self treated for this. Again as you diabetes you should not take any infection lightly.

I hope this helps and clarifies your concern, please feel free to ask again if you have something more to ask.